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Bauer, S. H.

Publications and source records attributed to Bauer, S. H..

18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Infrared Emissions from Shock Heated Hydrocarbons

The primary objective of this study was to ascertain whether low molecular weight hydrocarbons (LMWH) in the range C4 to C7, upon heating to temperatures above 900 K, emit IR radiations at frequencies that correspond to the 'unidentified infrared' (UIR) features - the recorded emissions from a variety of astronomical sources - reflection nebulae, HII regions, planetary nebulae, spiral galaxies and other extra galactic objects. We describe IR emission spectra recorded from shock-heated gases (C2H2; (H3C)2C = CH2; H2C = C(CH3) - C(CH3) = CH2; (H3C)2C = CH - C(CH3) = CH2), that arise from excitation of the fundamental C-H stretching vibrations. While the IR emissions from LMWH, anticipated over the entire spectra range, do not present a perfect match to UIR, the correspondence over several wavelength regions is better than the emissions anticipated from polycyclic aromatic hydrocarbon (PAH) species. Finally, we briefly review the range of proposals that have been presented for the origin of the UIR bands.

Stephens, K. M.↗
NASA NTRS1993

A piston-actuated shock-tube, with laser-Schlieren diagnostics

The essential construction features of a piston actuated shock tube are described, and its advantages relative to the conventional use of diaphragm ruptures for shock initiation are listed. Typical operational parameters are presented to illustrate the levels of reproducibility achieved. Tests with He and N2 drivers into about 99 percent Ar covered shock speeds from 1.539 +/- 0.002-0.8143 +/- 0.002 mm/microsec, corresponding to 2390-847 K incident shock temperatures. Application of this tube for recording postshock front density gradients of the endoergic dissociation of ethane and the exoergic condensation of iron atoms via the laser-Schlieren technique is described.

Hurst, S. M.↗
NASA NTRS1991

Estimation of homogeneous nucleation flux via a kinetic model

The proposed kinetic model for condensation under homogeneous conditions, and the onset of unidirectional cluster growth in supersaturated gases, does not suffer from the conceptual flaws that characterize classical nucleation theory. When a full set of simultaneous rate equation is solved, a characteristic time emerges, for each cluster size, at which the production rate, and its rate of conversion to the next size (n + 1) are equal. Procedures for estimating the essential parameters are proposed; condensation fluxes J(kin) exp ss are evaluated. Since there are practical limits to the cluster size that can be incorporated in the set of simultaneous first-order differential equations, a code was developed for computing an approximate J(th) exp ss based on estimates of a 'constrained equilibrium' distribution, and identification of its minimum.

Wilcox, C. F.↗
NASA NTRS1990

Time resolved spectra in the infrared absorption and emission from shock heated hydrocarbons

The wavelength range of a previously constructed multichannel fast recording spectrometer was extended to the mid-infrared. With the initial configuration, light intensities were recorded simultaneously with a silicon-diode array simultaneously at 20 adjacent wavelengths, each with a 20-micron time resolution. For studies in the infrared, the silicon diodes were replaced by a 20-element PbSe array of similar dimensions, cooled by a three-stage thermoelectric device. It is proposed that infrared emissions could be due to shock-heated low molecular-weight hydrocarbons. The full Swan band system appeared in time-integrated emission spectra from shock-heated C2H2; no soot was generated. At low resolution, the profiles on the high-frequency side of the black body maximum show no distinctive features. These could be fitted to Planck curves, with temperatures that declined with time from an initial high that was intermediate between T5 (no conversion) and T5(eq).

Bauer, S. H.↗
NASA NTRS1971

Shock synthesis of amino acids in simulated primitive environments.

A single pulse shock tube of a uniform bore was used in the experiments. The reaction mixture consisted of 3.3 per cent methane, 11 per cent ethane, and 5.6 per cent ammonia, diluted with ultra-pure argon. The formation of glycine, alanine, valine, and leucine under conditions of shock heating was observed. Thermodynamic relations are discussed together with questions of conversion efficiency.

Bar-Nun, A.↗
NASA NTRS1966

Association of CN in an expansion wave.

Kinetics of CN radicals association generated by shocking cyanogen-argon mixtures at high temperatures in reflected shock region of expansion wave

GAS MIXTURE↗
NASA NTRS1965

Thermal decomposition of clcn.

Shock tube study of thermal decomposition of cyanogen chloride using specific cyanide absorption spectroscopy

CHEMICAL KINETICS↗